From the linked study:

"While non-organic sexual dysfunctions have been presumed psychological in origin, and therefore the province of mental health experts, the unexplained sexual dysfunctions now rising sharply in young men (ED, difficulty orgasming, low sexual desire) are, to the extent they are reversible by quitting Internet pornography, not arising from “performance anxiety” (that is, psychosexual dysfunction, ICD-9 code 302.7), although performance anxiety may certainly accompany them."

It seems they fall short of saying porn is "making" these men impotent, but rather that quitting porn does improve the situation.